The present intention relates to a lubricating device which discharges lubricating oil to a spindle apparatus provided in various high-speed rotary machines such as a machine tool and, especially, to the bearing of the spindle.
Conventionally, in lubricating the bearing of a high-speed rotary spindle, normally, there are used lubricating devices of various types such as an oil mist type, an oil-air type, and a jet type.
The lubricating device of an oil mist type comprises an oil tank, a pump, a plunger, a pressure divider, compressed air, an electromagnetic valve, and a nozzle; and, in this device, lubricating oil is turned into a fine mist-like form, it is delivered through an air pipe using the compressed air, and it is jetted out to the interior portion of the bearing.
The lubricating device of an oil-air type comprises an oil tank, a pump, a distributor, a compressed air source, a plunger, and a nozzle; and, in this device, lubricating oil drops (0.01-0.03 ml) adjusted to a given quantity by the mechanical mechanism of the plunger is discharged into an air pipe, is delivered up to the nozzle by the compressed air, and is jetted out to the interior portion of the bearing.
The lubricating device of a jet type is a device which does not use the air source but turns lubricating oil into high pressure one using a high-pressure pump and jets out the high-pressure lubricating oil at a high speed into the interior portion of the bearing from a nozzle of which discharge diameter is narrowed.
By the way, while a current trend requests an increase in the rotation speed of the spindle device, in the lubricating devices of various types used for lubrication of the spindle device, there are found the following problems:
Firstly, in the lubricating device of an oil mist type, due to use of the compressed air, not only there arises a noise problem but also the mist-like lubricating oil scatters into the air to worsen an operation environment. Also, because of the scattering of the mist-like lubricating oil into the air, the quantity of lubricating oil to be supplied to the interior portion of the bearing is indefinite. Especially, in case where the bearing is rotated at a high speed, due to the effect of an air curtain, when dmxc2x7N is equal to or larger than 2000000 (dm expresses the pitch circle diameter of the bearing (mm), and N expresses the rotation speed (minxe2x88x921) of the bearing), the lubricating oil can be little supplied to the interior portion of the bearing, thereby raising a fear that the bearing can cause seizure.
In the lubricating device of an oil-air type, similarly to the above-mentioned oil mist type lubricating device, since the compressed air is used, not only there arises a noise problem but also the mist-like lubricating oil scatters into the air to thereby worsen the operation environment. Also, in the high-speed rotation of the bearing, as the result of the rotation of the spindle, there is produced an air curtain. Therefore, similarly, the lubricating oil can be little supplied to the interior portion of the bearing, thereby raising a fear that the bearing can cause seizure.
Also, in the lubricating device of an oil-air type, because it is difficult to supply a fine amount of lubricating oil continuously and stably, the lubricating oil must be supplied intermittently and thus the lubricating oil is supplied at a given quantity (normally, in the range of 0.01-0.03 ml) every given interval time (normally, in the rage of 8-16 min.) into the air pipe. Therefore, since the quantity of lubricating oil to be supplied to the interior portion of the bearing varies every given time, the lubricating condition of the interior portion of the bearing varies all the time and, especially, just after the lubricating oil is supplied, a large quantity of lubricating oil enters the interior portion of the bearing, thereby causing a phenomenon that the torque of the bearing and the temperature of the bearing can vary. There is a fear that this phenomenon can have ill effects on the working precision of a machine tool.
On the other hand, in a lubricating device of a jet type, when compared with the above lubricating devices of oil mist and oil-air types, there is little found the effect of the above-mentioned air curtain but, not only because there is required an attendant device such as a high-pressure pump but also because the quantity of lubricating oil to be supplied to the bearing increases to thereby increase drag resistance, there is necessary a large motor which is used to drive the spindle, which results in the increased cost.
As a device which has solved the difficulty in the above-mentioned fine quantity adjustment of a lubricant, there are known devices which are respectively disclosed in the following patent publications.
That is, in Japanese Patent Examined Publication No. 2-15003 of Heisei, there is disclosed a device for supplying a fine fixed quantity of liquid. In this supply device, a piezo-electric element is used to allow the fine quantity adjustment of the liquid and a lubricant is delivered to a nozzle by compressed air.
In a flow control valve disclosed in Japanese Patent Examined Publication No. 7-65695, a diaphragm is disposed in one end of a magnetostrictive element and an orifice is adjusted by the expansion and contraction of the magnetostrictive element to thereby adjust the flow quantity and pressure of fluid.
In a giant magnetostrictive material pump disclosed in Japanese Patent Unexamined Publication No. 3-222877 of Heisei, the displacement of a giant magnetostrictive material is enlarged by a lever, and a diaphragm is driven by the lever to turn the pressure of the interior portion of the pump into a negative pressure or a positive pressure, thereby sucking or discharging a fluid.
In a magnetic precision pump (Magnetostrictive Pump) disclosed in U.S. Pat. Nos. 4,795,318 and 4,804,314, in the interior portion of a cylinder, there is disposed a piston which is formed of a magnetostrictive material and a voltage is applied to a coil, which is disposed in such a manner that it encloses the piston, to thereby expand and contract the piston so as to discharge a fluid in the interior portion of the cylinder.
In a giant magnetostrictive material type injection-pump disclosed in Japanese Patent Unexamined Publication No. 4-81565 of Heisei, a needle valve is opened and closed by a giant magnetostrictive material to thereby inject a fixed quantity of high-pressure liquid.
However, in the above-mentioned pump using a giant magnetostrictive material or flow control valve, there are found the following problems.
The fine fixed quantity liquid supply device disclosed in Japanese Patent Examined Publication No. 2-15003 of Heisei has not solved yet a drawback caused by delivering the lubricant to the nozzle using the high-pressure air.
In the flow control valve disclosed in Japanese Patent Examined Publication No. 7-65695, the diaphragm area, to which the pressure of the liquid is applied, is larger than the sectional area of the giant magnetostrictive material and the liquid pressure is smaller than the pressure of the giant magnetostrictive material.
In the giant magnetostrictive material pump disclosed in Japanese Patent Unexamined Publication No. 3-222877 of Heisei, since the displacement is enlarged by the lever, the liquid pressure is smaller than the pressure of the giant magnetostrictive material. The output of the giant magnetostrictive material increases as a magnetic field by a coil is increased. However, in case where the coil magnetic field is increased, the required volume of the coil increases accordingly. As a result of this, a device using such coil increases in size.
In the magnetic precision pump disclosed in U.S. Pat. Nos. 4,795,318 and 4,804,314, since the piston itself is made of a drive element, the pressure of the lubricant cannot be made larger than the pressure of the giant magnetostrictive material.
The giant magnetostrictive material type injection pump disclosed in Japanese Patent Unexamined Publication No. 4-81565 of Heisei does not have a function to turn the pressure of the liquid into high pressure.
Further, in the oil-air lubricating method, there is used a fixed-quantity valve which is capable of mixing lubricating oil of the order of 0.01-0.03 ml per shot with air at given time intervals. As an example of the fixed-quantity valve, for example, there is known a valve which is disclosed in JP-B-8-2578U. This type of fixed-quantity valve is conventionally structured such that a fixed quantity of lubricating oil can be stored therein and can be discharged therefrom by making use of the reciprocating motion of a piston; specifically, the lubricating oil is stored in a cylinder disposed on one side of the piston and the lubricating oil is discharged on the opposite side of the piston. To reduce the oil discharge quantity, there can be expected a technique of reducing the diameter and stroke of the piston. However, in the conventional oil-air lubricating method, there are dimensional limits, for example, the sizes of sealing parts such as an O-ring and the size of a return spring, which makes it difficult to reduce the diameter and stroke of the piston. For this reason, it has been believed difficult to discharge a quantity of less than 0.01 ml of lubricating oil.
In addition, since the conventional lubricating apparatus employing the above-mentioned oil-air lubricating method is structured such that a given quantity of lubricating oil is stored therein and is discharged therefrom by use of the reciprocating motion of a single piston, a supply oil quantity per shot is normally large, that is, of the order of 0.03 ml and the lubricating oil is discharged at time intervals of approx. 15 min., thereby raising a problem that the temperature of the constantly rotating bearing can pulsate at the oil shot intervals. Also, in some cases, there are generated whizzing sounds between the rolling bodies and the mixed oil-air. The whizzing sounds between the rolling bodies and the mixed oil-air, when their frequencies are in the range of 2-3 KHz or less, in most cases, provide harsh noises. This raises a problem even in the case of a spindle which does not rotate at a very high speed, that is, when the product (dmxc2x7N) of the shaft diameter [mm] and the shaft rotation speed [minxe2x88x921] is 1500000 or less.
On the other hand, regarding a pipe structure for supply of a fine quantity of lubricating oil, FIG. 4 shows a lubricating apparatus of an oil-air type using an air flow as a medium. As the state of connection of the end faces of two housings is shown in FIG. 85A, a pipe passage 902 serving as an oil flow passage formed in a housing is sealed by O-rings 904 which are disposed on the housing end faces. Also, as the state of connection between the nozzle frame 906 and pipe passage 902 is shown in FIG. 85B, oil-air is supplied to the nozzle frame 106 through the pipe passage 902. However, in the case of a fine quantity of lubricating oil being supplied, in a pipe arrangement structure using such O-rings 104, when the lubricating oil is jetted out, the volume of the interior portion of the pipe passage is caused to vary due to the elastic deformation of the O-rings 904, which makes it impossible to supply a given quantity of lubricating oil.
The present invention airs at eliminating the drawbacks found in the above-mentioned circumstances. Accordingly, it is an object of the invention to provide a lubricating device which injects a high-precision set fine quantity of lubricant onto the lubricating surface of a rotary body at a high speed to thereby minimize an increase in torque and bearing temperature so as to be able not only to provide high torque stability and reduce the generation of noises but also to reduce the size and cost thereof, and a spindle apparatus using such lubricating device.
In attaining the above object, according to the invention, there is provided a spindle apparatus comprising a shaft, at least two bearings disposed spaced apart from the shaft in the axial direction of the shaft, each of the bearings having an inner race fitted with the shaft, and a housing fitted with the outer races of the bearings, with the inner races and outer races of the bearings being rotatable with respect to each other with rolling elements between them, the spindle apparatus further including: a lubricating device for supplying lubricating oil to the bearings at a discharge speed in the range of 10 m/sec.-100 m/sec. and in a fine discharge oil quantity in the range of 0.0005 ml/shot-0.01 ml/shot.
According to the above structure, since the discharge speed of the lubricating oil to be discharged from the nozzle is high, that is, 10 m/sec-100 m/sec., the lubricating oil can be supplied to the interior portion of the bearing positively without being influenced by an air curtain which can occur in the high-speed rotation. Also, because the discharge quantity of the lubricating oil is fine, that is, in the range of 0.0005 ml/shot-0.01 ml/shot, an increase in the temperatures of the bearings can be controlled down to a low level. Further, since there are not used attendant devices including a high-pressure pump such as a jet type, there is eliminated an increase in drag resistance which could be caused due to an increase in the quantity of the oil supplied to the bearings, so that, as a motor for driving the spindle, there can be used a motor which is inexpensive and compact.
Also, in addition to the above structure, there may be disposed a shaft rotation speed detector (tachometer) for detecting the shaft rotation speed. In this case, by controlling the supply interval and supply quantity of the lubricating oil discharged from the lubricating device based on the detect results of the shaft rotation speed detector (tachometer), a proper oil quantity of lubrication is possible with respect to the spindle rotation regardless of the spindle rotation speed, so that an ideal lubricating condition can be always obtained in the interior portion of the bearing. Also, the increase in the bearing temperature can also be controlled down to a further lower level. Further, since the lubricating oil is supplied to the interior portion of the bearing positively, a lubricating oil supply efficiency can be enhanced and the lubricating oil consumption can be reduced. Moreover, since compressed air supplied by a compressor is not used as in the lubricating device of an oil mist system or an oil-air system, the noise level is low and the oil mist can be little produced.
And, in addition to the above structure, there may be disposed a lubricating oil filter, an air bleeding sensor, and a clogging detect pressure sensor. In this case, there can be avoided troubles such as a clogged condition.
Further, in addition to the above structure, there may be disposed a multi-branch piping device (a multi-distribution mechanism) between a superfine quantity oil lubricating pump and the nozzle, for distributively supplying lubricating oil from the superfine quantity oil lubricating pump to the plurality of bearings, so that the lubricating oil is supplied to each bearing from the multi-branch piping device.
With this structure, the lubricating oil supplied from the superfine quantity oil lubricating pump is distributively supplied to each bearing stably without reducing the discharge speed and the discharge quantity, and without causing vibrations of the discharge speed and the discharge quantity. Further, this structure provides a supply of the lubricating oil for the spindle apparatus having a plurality of bearings with only a lubricating apparatus.
That is, according to the present spindle lubricating apparatus, thanks to the multi-distribution mechanism, not only a fine quantity of lubricating oil can be distributively supplied to the plurality of bearings at the discharge speed of 10 m/sec.-100 m/sec. in a discharge quantity of 0.0005 ml/shot-0.01 ml/shot accurately and stably, but also the structure of the spindle lubricating apparatus can be made simple and compact. Therefore, an ideal lubricating state can be always obtained in each of the bearings, the stability of the bearing torque can be enhanced, and an increase in the bearing temperature can be controlled down to a low level.
Also, the multi-distribution mechanism includes a distribution housing having such a number of lubricating oil supply holes as to corresponds to the number of distribution of the lubricating oil, a rotor valve which can be rotatably contacted with the distribution housing to thereby bring a flow passage into communication with the lubricating oil supply holes sequentially, and a motor for rotating the rotor valve.
More specifically, in the distribution housing, the lubricating oil supply holes are disposed in a circular ring manner, and a center flow passage is formed in the center of this circular ring. The rotor valve has a groove serving as a flow passage in such a manner that it extends from the center of rotation thereof up to a diameter position larger than a pitch circle diameter (PCD) at the positions of the lubricating oil supply holes.
According to this structure, in case where the rotor valve is rotated, the center flow passage and lubricating oil supply holes of the distribution housing are allowed to communicate with each other by the groove of the rotor valve sequentially, so that the lubricating oil can be supplied to the respective lubricating oil supply holes.
Also, the distribution housing may also be structured such that such a number of longitudinal holes as to corresponds to the number of bearings (number of distributions) are formed in the radial direction thereof and lubricating oil supply holes are formed so as to extend from the thrust direction thereof as well as be in phase with and penetrate through the longitudinal holes.
According to this structure, when the center flow passage and lubricating oil supply holes of the distribution housing are made to communicate with each other, the lubricating oil can be supplied to the radial-direction longitudinal holes.
Further, the distribution housing may also be structured in the following manner: that is, such a number of lubricating oil supply holes as to corresponds to the number of bearings (number of distributions) are formed such that they can be made to communicate with the groove formed in the rotor valve from a direction oblique with respect to the axial direction of the distribution housing.
According to this structure, since the lubricating oil supply holes are formed in the oblique direction with respect to the axial direction of the distribution housing, the projecting amount of the distribution housing in the radial direction is reduced, thereby being able to provide a structure which is excellent in space efficiency.
And, the multi-distribution mechanism may also be composed of a distribution housing having such a number of lubricating oil supply holes as corresponds to the number of distributions, a rotor valve which can be rotatably contacted with the distribution housing to thereby bring a flow passage into communication with the lubricating oil supply holes sequentially, a shaft for rotationally driving the rotor valve, a spring member for energizing the shaft toward the rotor valve side, and a thrust bearing for supporting the shaft in a freely rotatable manner.
According to this structure, while reducing the rotation resistance by the thrust bearing, the elastic compression force of the spring member can prevent the lubricating oil from leaking from the contact portions between the rotor valve and distribution housing, so that the lubricating oil can be positively supplied from the groove of the rotor valve to the lubricating oil supply holes of the distribution housing.
By the way, the oil supply quantity to the interior portion of the bearing, in case where dmxc2x7N is equal to or larger than 1000000, preferably, may be in the range of 0.0005 ml/min.-0.12 ml/min., and, more preferably, in the range of 0.003 ml/min.-0.12 ml/min.
Also, the inside diameter of the nozzle outlet, preferably, may be in the range of 0.08 mm-0.6 mm and, more preferably, in the range of 0.1 mm-0.5 mm.
Further, a ratio of the length L (mm) of the pipe up to the nozzle to the pipe diameter d (mm), preferably, may be 5xe2x89xa6L/d4xe2x89xa612000 mmxe2x88x923, and, more preferably, 5xe2x89xa6L/d4xe2x89xa610000 mmxe2x88x923.
Still further, according to another aspect of the invention, there is provided a lubricating device which uses a magnetostrictive pump including a pump chamber for pressurizing lubricant by means of the expanding and contracting operations of a rod body formed of magnetostrictive material to be executed by applying a magnetic field to the rod body and removing the magnetic field therefrom, thereby discharging the pressurized lubricant, the lubricating device comprising: a check valve disposed in the intermediate portion of a flow passage for supplying the lubricant to the magnetostrictive pump to prevent the lubricant from flowing out from the magnetostrictive pump, and a nozzle disposed on the lubricating discharge side of the magnetostrictive pump and having a flow passage sectional area smaller than the lubricant flow passage sectional area of the check valve.
According to the present lubricating device, the rod body can be expanded due to the application of the magnetic field, and the lubricant within the magnetostrictive pump can be thereby compressed. Due to the compression of the lubricant, the pressure of the flow passage for supplying the lubricant is increased, the check valve is closed, and the lubricant is discharged externally at a high speed from the nozzle. In case where the magnetic field application is cut off, the rod body is contracted to thereby increase the internal capacity of the pump, so that the lubricant is supplied into the pump through the check valve. In this operation, the air also flows in from the leading end of the nozzle. However, since the flow-in quantity ratio of the lubricant to the air is proportional to the square of the flow passage sectional area ratio of the check valve to the nozzle, the flow-in quantity of the lubricant becomes larger than that of the air, so that, in the next operation as well, the lubricant can be discharged similarly.
Further, according to the above lubricating device, the one end side of the rod body is fixed, a piston is connected to the other end side of the rod body, and the piston is slidably disposed within a cylinder to thereby form a pump chamber, while the cross sectional area of the inner surface of the cylinder is set smaller than the cross sectional area of the rod body.
In the present lubricating device, due to the expansion and contraction of the rod body, the piston within the cylinder is moved to thereby form the pump. And, the pressure of the lubricant within the cylinder is higher than the pressure generated by the rod body, which makes it possible to discharge the lubricant at a high speed.
Also, in the lubricating device, the decreased area of the pump chamber due to the expansion of the rod body is set equal to the sum of the quantity of the air flowing in from the nozzle when the rod body is contracted, a decreased volume due to compression of the lubricant that is present within the internal capacity between the check valve and the outlet of the nozzle, the increased capacity of the internal capacity due to the pressure deformation of parts forming the internal capacity, and a required discharge quantity of lubricant.
In the lubricating device, the magnetic field to be applied to the rod body is controlled while correcting it using values with variable elements taken into account, while the variable elements respectively relate to the quantity of air flowing in from the nozzle, the decreased volume due to the compression of the lubricant, and the increased capacity of the internal capacity due to the pressure deformation of parts forming the internal capacity. This can avoid a discharge quantity error which could otherwise be caused by the variable elements, so that a desired discharge quantity can be obtained with high accuracy.
Further, in the lubricating device, the magnetostrictive pump includes a coil for applying a magnetic field and a control device for controlling a current to be supplied to the coil to thereby expand and contract the rod body; and, the control device, in the initial excitation stage of the coil, supplies a current until the lubricant within the pump chamber reaches such a pressure as to allow the magnetostrictive pump to obtain a desired discharge speed, after reaching this pressure, supplies a current for maintaining the pressure of the lubricant constant according to the discharge quantity of the lubricant, and further, after a desired lubricant discharge quantity is obtained, cuts off the supply current.
According to the present lubricating device, when the current is supplied to the coil from the control device, the rod body is expanded to thereby allow the piston to compress the lubricant within the pump chamber. As a result of this, the pressure within the cylinder is increased, the suction valve is closed, and the lubricant is thereby discharged externally at a high speed from the nozzle. At the then time, the control device, for example, in the initial excitation stage of the coil, supplies a current to the coil until the current reaches such a current value for the magnetostrictive pump as to be able to obtain a desired discharge speed, that is, the control device raises the current up to this current value quickly. During this, a high voltage is applied to the coil to thereby raise the current quickly against the time constant of the coil. And, after reaching the current value to be able to obtain the desired discharge speed, in order to maintain the pressure of the lubricant which decreases according to the discharge quantity of the lubricant constant, the control device supplies the current in such a manner that the capacity of the cylinder decreases by a capacity equal to the discharge quantity of the lubricant. During this, due to the time constant of the coil, the voltage is switched over to a voltage which can obtain a desired current increasing speed. Next, after the desired lubricant discharge quantity is obtained, the supply current to the coil is cut off. Thanks to this, a required lubricant pressure can be obtained in and from the early discharge stage of the lubricant and, after the start of discharge of the lubricant, the discharge speed can be maintained constant, so that the discharge of the lubricant can be carried out accurately and stably. Also, when the current is cut off, the rod body is contracted to thereby increase the internal capacity of the pump chamber, so that the lubricant can be supplied into the pump chamber through the suction valve.
Also, the above lubricating device further includes a measuring device for measuring any one of the value of a current to be supplied to the coil, a voltage value proportional to this current, and the value of a magnetic flux caused by this current; and, an abnormal condition judging device for comparing a measured value with respect to an elapsed time measured by the measuring device with a measured value in a normal condition time to thereby judge whether an abnormal condition has occurred or not, whereby, when the abnormal condition judging device judges that an abnormal condition has occurred, the lubricating device issues an abnormal signal.
According to the present lubricant device, for example, assuming that a target to be measured is a current value, in case where a current value measured at the time when a certain time has passed after the start of the supply of a current is larger than a current value (a design value) in a normal operation time, that is, in case where a time required for a current to increase up to a certain current value is shorter than a design value, it can be judged that an abnormal condition such as the clogged condition of the nozzle has occurred. On the other hand, in case where the current value measured at the time when a certain time has passed after the start of the supply of the current is smaller than the design value, that is, in case where the time required for the current to increase up to a certain current value is longer than the design value, it can be judged that an abnormal condition such as lubricant leakage has occurred. Also, assuming that the target to be measured is a voltage value or a magnetic flux value, an abnormal condition can be judged similarly. And, by issuing the abnormal signal at the time when the abnormal condition occurs, feedback control can be carried out, for example, the operation of the supply target of the lubricant can be stopped.
Further, the above-mentioned lubricating device further includes a measuring device for measuring any one of the value of a current to be supplied to the coil, a voltage value proportional to this current, and the value of a magnetic flux caused by this current; and, an air mixture judging device for comparing a measured value with respect to an elapsed time measured by the measuring device with a measured value in an air non-mixture time to thereby judge whether the air is mixed or not, whereby, in the start of the operation of the lubricant device, until the air mixture judging device judges that the air is not mixed, the lubricant device increases the current to be supplied to the coil or increases the supply frequency of the current.
According to the present lubricating device, assuming that the target to be measured is a currents in case where the air is mixed into the lubricant, the rising time of the current to be measured is long, which makes it possible to judge the presence or absence of the mixed air. Also, assuming that the target to be measured is a voltage value or a magnetic flux value, an abnormal condition can be judged similarly. And, in the start of the operation of the lubricating device, until it is judged that the mixed air is not present, by increasing the current to be supplied to the coil or by increasing the supply frequency of the current, or by increasing both the current and the supply frequency of the current, the discharge quantity and discharge cycle of the magnetostrictive pump can be increased, so that the lubricant can be quickly sucked into the pump from the tank and the air bleed can be completed in a short time.
To sum up the above facts, by using the super fine quantity oil lubricating system, a lubricating oil forced circulating device, a heat exchanger, a lubricating oil collecting device, and other attendant devices such as compressed air, which are used in the conventional lubricating systems such as a lubricating system of an oil mist, a lubricating system of an oil-air type and a lubricating system of a jet type, can be simplified; the noise level can be controlled down to a low level, which can be consideration for environment. And, the consumption of the lubricating oil can be reduced, the bearing torque can be enhanced in stability, and the bearing temperature increase can be controlled down to a low level, thereby being able to enhance the rotation accuracy of the spindle. Therefore, according to the present invention, there can be provided a spindle apparatus which is more advantageous than the conventional spindle apparatus using the related lubricating methods.
Further, the lubricating apparatus for discharging a fine quantity of lubricating oil from a nozzle directly to the interior portion of a bearing at given time intervals at a high speed, may includes: a pump having a larger discharge quantity than that from the nozzle; and, a switch valve interposed between oil pipes for connecting together the pump and nozzle and structured such that, in case where a discharge oil pressure from the pump is less than a given pressure, it shuts off the oil pipes to thereby stop the discharging of the lubricating oil from the nozzle, in case where the discharge oil pressure from the pump is equal to or more than the given pressure, it opens the oil pipes to thereby allow the lubricating oil supplied from the pump to be discharged from the nozzle for a given period of time, and it is capable of repeating the execution of this series of operations.
According to the present lubricating apparatus, in case where a discharge oil pressure from the pump is less than a given pressure, the switch valve shuts of f the oil pipes to thereby stop the discharging of the lubricating oil from the nozzle and, on the other hand, in case where the discharge oil pressure from the pump is equal to or more than the given pressure, the switch valve opens the oil pipes to thereby allow the lubricating oil supplied from the pump to be discharged from the nozzle for a given period of time. Therefore, without using an expensive fine quantity lubricating pump using an electromagnet or a giant-magnetostrictive material, a sufficient discharge speed can be obtained using an inexpensive pump and thus, in a spindle which is rotated at a high speed, stable lubricating characteristics, that is, enhanced seizure resistance and reduced torque variations can be realized. Also, it is possible to eliminate the generation of the whizzing noises of the rolling bodies that raises a problem in the conventional oil-air and oil mist lubricating methods. Further, in the portion of the pipe that extends up to the switch valve, there can be used a resin-made pressure resisting tube, which can enhance the design freedom of the pipe arrangement.
And, in the lubricating apparatus, preferably, the discharge quantity of lubricating oil to be discharged from the nozzle per shot may be in the range of 0.0001-0.01 ml.
In the lubricating apparatus, since the discharge quantity of lubricating oil to be discharged from the nozzle per shot is set larger than 0.0001 ml, it is possible to prevent the lowered flow speed of the lubricating oil which could be caused under the great influence of the compression characteristic of the lubricating oil, the pressure deformation of the pipes, and the response characteristic of the switch valve; that is, a sufficient flow speed can be obtained. Also, since the discharge quantity of lubricating oil to be discharged from the nozzle per shot is set smaller than 0.01 ml, torque variations occurring in the bearing can be prevented.
Also, the discharge speed of the lubricating oil to be discharged from the nozzle, preferably, may be set equal to or more than 10% of the peripheral speed of the inner ring of the bearing.
According to the thus structure, since the discharge speed of the lubricating oil to be discharged from the nozzle is set equal to or more than 10% of the peripheral speed of the inner ring of the bearing, there can be secured a discharge speed necessary for the lubricating oil to reach the interior portion of the bearing. As a practical advantage, the lubricating apparatus can use an inexpensive oil pressure pump having a pump pressure of the order of 2.5 MPa.
Further, the opening time of the switch valve may be preferably set in the range of 0.1-50 ms.
With the above structure, a required discharge quantity of 0.0001-0.01 ml can be satisfied. That is, in case where the pump pressure, lubricating oil and pipes are set according to the following expressions, the relationship between the opening time t of the switch valve and discharge quantity can be determined and thus the opening time t of the switch valve, which is requested to meet the required discharge quantity of 0.0001-0.01 ml, can be set in the range of 0.1-50 ms.
v=Cdxc2x7(2(pxe2x88x92xcex94p)/xcfx81)0.5 
q=vxc2x7xcfx80d2xc2x7t/4 
xcex94p=32xc2x7xcexcxc2x7Lxc2x7d2v/D4 
where, Cd expresses a flow coefficient, p: a pump pressure (Pa), xcex94p: a pressure loss (Pa), xcfx81: a lubricating oil density (kg/m3), d: a nozzle diameter (m), t: the opening time (s) of the switch valve, xcexc: a lubricating oil viscosity coefficient (Paxc2x7s), L: a pipe length (m), and D: a pipe inside diameter (m), respectively
Also, the lubricating apparatus may also be structured such that the switch valve includes a fixed member having a fixed sliding contact surface and a rotary member which has a movable sliding contact surface to be closely contactable with the fixed sliding contact surface and rotates the movable sliding contact surface in sliding contact with the fixed sliding contact surface about an axial line perpendicular to the fixed sliding contact surface. In the fixed sliding contact surface of the fixed member, more specifically, on the circumference of the fixed sliding contact surface with the axial line as the center thereof, there are opened up a discharge hole to be connected to the pump and an oil feed hole to be connected to the nozzle. And, in the movable sliding contact surface of the rotary member, more specifically, on the circumference of the movable sliding contact surface with the axial line as the center thereof, there is formed an arc-shaped slit having a center angle larger than at least a center angle formed between the discharge hole and oil feed hole.
According to the thus-structured lubricating apparatus, in case where the rotary member of the switch valve is rotated with respect to the fixed member thereof and the arc-shaped slit formed in the movable sliding contact surface of the rotary member is matched to the discharge hole and oil feed hole respectively formed in the fixed sliding contact surface of the fixed member, the discharge hole and oil feed hole are allowed to communicate with each other through the arc-shaped slit. Therefore, only while the discharge hole and oil feed hole are both matched to the arc-shaped slit at the same time, the switch valve is opened (the oil pipes are opened), so that the lubricating oil from the pump can be discharged from the nozzle for a given period of time.
Also, the lubricating apparatus may be structured such as to have: a motor for rotating the rotary member; a pressure switch for detecting the discharge oil pressure of the pump; and, a controller which sends a drive signal to the pump, on receiving a detect signal from the pressure switch issued when the discharge oil pressure is equal to or more than a given pressure, sends a one-rotation drive signal to the motor, after then, sends a drive stop signal to the pump, and is capable of repeating the execution of this series of operations at given time intervals.
According to the thus-structured lubricating apparatus, in case where the pump is switched on by the controller, the oil pressure is raised; and, in case where the controller detects through the pressure switch that the oil pressure is equal to or higher than a given pressure, the controller rotates the motor once and, after then, the controller switched off the pump. This series of operations are executed repeatedly at given time intervals by the controller, whereby the lubricating oil from the pump can be discharged from the nozzle at given time intervals.
Also, the lubricating apparatus may be structured as follows. That is, the switch valve includes a fixed member having a fixed sliding contact surface and a rotary member which has a movable sliding contact surface closely contactable with the fixed sliding contact surface and rotates the movable sliding contact surface in sliding contact with the fixed sliding contact surface about an axial line perpendicular to the fixed sliding contact surface. In the fixed sliding contact surface of the fixed member, more specifically, on the circumference of the fixed sliding contact surface with the axial line as the center thereof, there are opened up a plurality of oil feed holes to be connected to the nozzle and, at the position of the axial line, there is opened up a discharge hole connected to the pump; and, in the movable sliding contact surface of the rotary member, there is formed a slit in such a manner that it extends from the axial line position along the radial direction of the rotary member up to the position of the oil feed hole.
According to the thus-structured lubricating apparatus, in case where the rotary member of the switch valve is rotated with respect to the fixed member thereof and the slit formed in the movable sliding contact surface of the rotary member is matched to the oil feed hole formed in the fixed sliding contact surface of the fixed member, the switch valve is opened (the oil pipes are opened), with the result that the lubricating oil from the pump can be discharged from the nozzle for a given period of time. In this case, since the plurality of oil feed holes are formed on the circumference of the fixed sliding contact surface, each time the rotary member is rotated, the lubricating oil from the discharge hole is supplied to the respective oil feed holes, that is, one rotation of the rotary member can supply the lubricating oil to a plurality of portions.
And, the lubricating apparatus may be structured in the following manner. That is, the switch valve includes a fixed member having a fixed sliding contact surface and a slide member which has a movable sliding contact surface closely contactable with the fixed sliding contact surface and reciprocates the movable sliding contact surface in the linear direction in sliding contact with the fixed sliding contact surface with respect to the fixed sliding contact surface. In the fixed sliding contact surface of the fixed member, there are opened up a plurality of discharge holes to be connected to the pump in such a manner that they are spaced from each other in the linear direction; and, in the movable sliding contact surface of the slide member, there are opened up a plurality of oil feed holes to be connected to the nozzle in such a manner that they are arranged in-the linear direction at the same intervals as the discharge holes.
According to the thus-structured lubricating apparatus, in case where the fixed member and slide member are reciprocated in the linear direction in sliding contact with each other and the plurality of discharge holes formed in the fixed sliding contact surface of the fixed member and the plurality of oil feed holes formed in the movable sliding contact surface of the slide member are allowed to communicate with each other or are shut off from each other at the same time, the lubricating oil from the pump can be discharged from the nozzle for a given period of time. That is, according to this lubricating apparatus, since the slide member is reciprocated in the linear direction in a sliding contact manner, a movable member of a solenoid serving as a drive source and a linear drive device such as a cylinder can be used as they are.
Still further, the lubricating apparatus may be structured in the following manner. That is, the switch valve includes: a cylindrical-shaped stator having a fixed sliding contact surface on the inner peripheral surface thereof; and, a rotor which has a rotary sliding contact surface to be closely contacted with the fixed sliding contact surface and rotates while the rotary sliding contact surface is in sliding contact with the fixed sliding contact surface. In the fixed sliding contact surface of the stator, there are opened up a plurality of oil feed holes to be connected to the nozzle in such a manner that they are spaced from each other in the inner peripheral circle direction; and, in the rotary sliding contact surface of the rotor, there are formed a plurality of discharge holes to be connected to the pump in such a manner that they are arranged in the outer peripheral circle direction at the same intervals as the oil feed holes.
According to the thus-structured lubricating apparatus, in case where the rotor is rotated within the stator and the plurality of oil feed holes formed in the fixed sliding contact surface of the stator are matched to the plurality of discharge holes formed in the rotary sliding contact surface of the rotor, the lubricating oil from the pump can be discharged from the nozzle for a given period of time. The stator and rotor can be structured in a movable fit manner, so that high-speed switching can be realized easily using low torque. For example, a rotary solenoid using a permanent magnet and an electromagnet can be used, a high-speed response characteristic can be obtained, a drive circuit can be simplified when compared with an ordinary motor, and the reduced cost of an actuator can be realized.
Moreover, the lubricating apparatus according to the present invention may includes: a pump for switching on and off the pressure of oil to be discharged to a hydraulic main pipe; a discharge cylinder in which a discharge piston is mounted, an oil supply chamber is formed on one end side of the discharge piston in the moving direction thereof, and a hydraulic chamber to be connected to the hydraulic main pipe is formed on the other end side of the discharge piston, while the discharge piston is disposed so as to be energized toward the hydraulic chamber side by spring means; a three-way valve connected to the hydraulic main pipe, an oil supply passage to be connected to the oil supply chamber, and an oil storage passage, for allowing the hydraulic main pipe and oil storage passage to communicate with each other when the oil pressure is switched on and, on the other hand, when the oil pressure is switched off and the oil pressure from the oil storage passage is given to the three-way valve, for allowing the oil storage passage and the oil supply passage to communicate with each other; and, an oil storage cylinder in which an oil storage piston is mounted and, on one end side of the oil storage piston in the moving direction thereof, there is formed an oil storage chamber to be connected to the oil storage passage, while the oil storage piston is disposed so as to be engergized toward the oil storage chamber side by spring means.
According to the present lubricating apparatus, since the discharge cylinder and oil storage cylinder are disposed separately, when compared with the conventional lubricating apparatus in which oil is stored within a cylinder disposed on one side end of a single piston and the oil is discharged on the opposite side, the limits on the dimensions of the seal member and return spring can be reduced, which can facilitate the reduction of the diameters of the discharge cylinder and oil storage cylinder. Also, due to provision of two pistons, the oil operation area of the discharge piston can be set larger than the oil pressurizing area, so that the discharge piston can be pushed with a large force and thus a high-speed stroke can be realized. As a result of this, when compared with a lubricating apparatus using an electromagnet or a giant-magnetostrictive material, a fine quantity of the order of 0.001 ml of oil can be discharged at a high speed using a low-cost and simple structure.
And, the lubricating apparatus may also be characterized in that, when the discharge port is closed and the oil pressure of the hydraulic main pipe is on, the oil pressure of the oil supply chamber becomes larger than the oil pressure of the hydraulic chamber.
According to the present lubricating apparatus, when the discharge port is closed and the oil pressure of the hydraulic main pipe is on, the oil pressure of the oil supply chamber becomes larger than the oil pressure of the hydraulic chamber, thereby being able to discharge oil at a high speed. That is, in the conventional lubricating apparatus using a single piston, due to the influence of the return spring for energizing the piston, the oil discharge pressure depending on the restitutive force of the return spring is always lower than the oil supply pressure obtained when the return spring is compressed. However, in the present lubricating apparatus, the oil pressure of the oil supply chamber (that is, oil discharge pressure) can be increased, with the result that discharging of oil at a high speed can be realized.
Also, the lubricating apparatus may also be structured such that, on the hydraulic chamber side of the discharge cylinder, there is mounted a drive piston movable by the oil of the hydraulic chamber to thereby push and drive the discharge piston, and the oil operation area of the drive piston is larger than the oil pressurizing area of the discharge piston.
According to the present lubricating apparatus, since the oil operation area of the drive piston is larger than the oil pressurizing area of the discharge piston, in case where the oil pressure from the hydraulic main pipe is applied to the drive piston, the discharge piston can be driven with a large force. Thanks to this, the high-speed stroke of the discharge piston can be realized and thus oil can be discharged from the discharge cylinder at a high speed.
Further, the lubricating apparatus may also be structured such that, between the discharge piston and drive piston, there is formed an idling section where the drive piston can be moved in a direction to approach the discharge piston.
According to the present lubricating apparatus, in case where the oil pressure from the hydraulic main pipe is applied to the drive piston, the drive piston is allowed to move the idling section by itself with no contact with the discharge piston. That is, without a start load which is otherwise generated in the start time of the drive piston due to its contact with the discharge piston, the drive piston is able to start under small movable resistance. Thanks to this, while the drive piston is moving in the idling section, the pressure of the oil pressure pump is raised up to a sufficient level, and there is generated inertia in the drive piston, so that the discharge piston can be driven with a large and high-speed force.
And, the lubricating apparatus may also be structured such that an umbrella valve is mounted in the three-way valve; and, the umbrella valve is structured such that, when the oil pressure is switched on, the main body of the umbrella valve closes the oil supply passage and a flexible umbrella piece disposed on the outer periphery of the umbrella valve main body is reduced in diameter to thereby allow the hydraulic main pipe and oil storage passage to communicate with each other and, on the other hand, when the oil pressure is switched off and the umbrella valve receives the oil pressure from the oil storage passage, the umbrella valve main body is moved in a direction to open the oil supply passage and the flexible umbrella piece is enlarged in diameter to thereby allow only the oil storage passage and oil supply passage to communicate with each other.
According to the present lubricating apparatus, in case where the oil pressure of the hydraulic main pipe connected to the three-way valve is switched on, the umbrella valve main body closes the oil supply passage and the flexible umbrella piece disposed on the outer periphery of the umbrella valve main body is reduced in diameter due to the present oil pressure, thereby allowing the hydraulic main pipe and oil storage passage to communicate with each other. Therefore, oil from the hydraulic main pipe reaches the oil storage cylinder through the oil storage passage, moves the oil storage piston against the energizing force of spring means for energizing the oil storage piston, and then flows into the oil storage chamber of the oil storage cylinder. That is, storage of the oil into the oil storage cylinder is completed. On the other hand, in case where the oil pressure of the hydraulic main pipe is switched off, the diameter reduced state of the flexible umbrella piece due to the oil pressure is removed and thus the flexible umbrella piece is enlarged in diameter, thereby shutting off the hydraulic main pipe and oil storage passage from each other. At the same time, due to the returning energizing force of the spring means for energizing the oil storage piston, the umbrella valve main body receives the oil pressure from the oil storage passage is thereby moved in a direction to open the oil supply passage. As a result of this, only the oil storage passage and oil supply passage are allowed to communicate with each other and the oil stored in the oil storage chamber is supplied through the oil storage passage and oil supply passage and is filled into the oil supply chamber of the discharge cylinder, thereby completing the preparation for the next discharging operation.
Also, the lubricating apparatus may also be structured such that, with the three-way valve, there is threadedly engaged an air bleeding plug for moving the umbrella valve in a direction to open the oil supply passage, or a stop plug in such a manner it can be removed from the three-way valve.
According to the present lubricating apparatus, on the three-way valve, there is disposed the air bleeding plug which can move the umbrella valve in a direction to open the oil supply passage. This air bleeding plug is used to deflate air within the portion of the pipe existing upstream of the oil supply passage. In order to be able to discharge a fine quantity of oil, it is important that the air within the pipe can be deflated completely. That is, in case where the oil discharge quantity is very small, it is difficult to deflate the air within the pipe only by repeating normal oil dischargings. Therefore, in case where the air bleeding plug having a fine pin in the leading end thereof is threadedly engaged with the three-way valve and oil when the oil pressure pump is switched on due to the movement of the umbrella valve is forced to flow into the oil supply passage, the air bleeding can be achieved simply. After completion of the air bleeding, the air bleeding plug is replaced with the stop plug and a normal operation is executed.
Also, the lubricating apparatus may also be structured such that lubricating oil of 0.0005-0.01 ml per shot is directly jetted to a rolling bearing at the discharge speed of 10% or more of the peripheral speed of the inner ring of the rolling bearing.
According to the present lubricating apparatus, a quantity of 0.0005-0.01 ml per shot of lubricating oil is directly jetted to the rolling bearing at the discharge speed of 10% or more of the inner ring peripheral speed of the rolling bearing. In lubrication of the rolling bearing, the discharge speed necessary for the lubricating oil to reach the interior portion of the bearing is about 10% of the inner race peripheral speed and, therefore, the discharge speed provided by the present lubricating apparatus is enough to lubricate the interior portion of the bearing.
Additionally, in the spindle apparatus according to the present invention, a pipe for supplying the lubricating oil is set such that a pipe parameter (Lxc2x7dn2/d4), which expresses the relationship between the length L of the pipe, a nozzle diameter dn (m), and a pipe inside diameter d (m), is smaller than 5xc3x97xe2x88x92104 [mxe2x88x921], and also that, the sum of the quantity of pipe expansion due to the pressure of lubricating oil in the interior portion of the pipe and the compression volume of the lubricating oil is equal to or less than the discharge quantity of said lubricating oil.
According to the spindle apparatus of the invention, when supplying a fine quantity of lubricating oil to the spindle apparatus, the pipe for the lubricating oil is set so as to satisfy the given conditions. Thanks to this, even when the present invention is applied to a spindle apparatus which is narrow and limited in the space for installation of a nozzle and arrangement of the pipe, the nozzle and pipe can be disposed in a compact structure, so that a fine quantity of lubricating oil can be supplied accurately and stably and, at the same time, generation of noises due to the whizzing sounds and poor lubrication due to the air curtain, which have been problems to be solved in the conventional oil-air lubricating apparatus, can be prevented.
In more detail, the present spindle apparatus is structured such that, the nozzle frame for jetting out the lubricating oil to the given positions of the interior portion of the spindle apparatus and the lubricating apparatus are connected together by the pipe which satisfies the following conditions:
pipe outside diameter D: 1.0xc3x9710xe2x88x923-3.2xc3x9710xe2x88x923 [m]
pipe inside diameter d: 0.8xc3x9710xe2x88x923-2.0xc3x9710xe2x88x923 [m]
Young""s modulus of pipe material: 3 [GPa] or more
Pipe length L:
L greater than 0.5 [m]
Lxc2x7dn2/d4 less than 5xc3x97104 [mxe2x88x921]
Lxc2x7pxc2x7{xcfx80xc2x7d2/(4K)+xcfx80xc2x7d2xc2x7{(D2+d2)/(D2xe2x88x92d2)+xcexd}/(2E)} less than q[m3]
where,
dn: nozzle diameter (0.08xc3x9710xe2x88x923-0.3xc3x9710xe2x88x923 [m])
K: bulk modulus [Pa] of lubricating oil
xcexd: Poisson""s ratio of pipe material
p: average pressure [Pa] in pipe
q: discharge quantity [m3].
Also, the present spindle apparatus is a spindle apparatus having a cooling function using a jacket cooling system. In the jacket cooling system, as a thermal displacement measure, cooling oil is charged into an outer housing (outer cylinder) of a bearing (outer cylinder cooling system).
According to the present spindle apparatus, even in the case of a spindle apparatus of a jacket cooling system being narrow and limited in the space for arrangement of a pipe for lubricating oil and installation of a nozzle, a fine quantity of lubricating oil can be supplied.
The present spindle apparatus may be structured such as to include a spindle shaft, a plurality of rolling bearings for supporting the spindle shaft in a freely rotatable manner, an inner housing for covering the outside of the rolling bearings, and an outer housing for covering the outside of the spindle apparatus; and, a pipe is arranged so as to extend from the lubricating apparatus up to a nozzle frame disposed within the inner housing through a communication hole for supply of lubricating oil formed in the outer housing along the axial direction thereof and also through an opening formed in the inner housing.
And, the present spindle apparatus is also structured such that the pipe is connected to the nozzle frame in the axial direction of the housing.
According to the present spindle apparatus, even in a structure which cannot provide a space for arrangement of a pipe in a direction perpendicular to the axial direction of the housing, the pipe can be installed by arranging the pipe in the axial direction of the housing.
Also, the pipe may also be connected from the lubricating apparatus to the nozzle frame through an opening formed in the inside diameter surface of the outer housing.
In this case, even in a structure which cannot provide a space for arrangement of a pipe in the axial direction of the spindle shaft, the pipe can be installed by arranging it in a direction perpendicular to the axial direction of the housing.
Further, in the present spindle apparatus, the inner housing may includes a first inner housing to which the outer races of the rolling bearings are to be fixed, and a second inner housing including an insertion portion for storing therein the first inner housing in the axial direction thereof, while the inside diameter of the inner peripheral surface of the insertion portion of the second inner housing is set larger than the outside diameter of the outer peripheral surface of the first inner housing.
According to this structure, when the first inner housing is inserted into the second inner housing in the axial direction thereof, since the pipe cannot be caught by and between them, the first inner housing can be inserted smoothly. Thanks to this, even in the deep and limited-space portion of the spindle apparatus, the pipe can be arranged while the spindle apparatus is structured so as to be easy to assemble.
Also, in case where a cut-out groove for arrangement of the pipe is formed in the insertion portion of the second inner housing, when the first housing is slid in the axial direction, the pipe can be stored in the cut-out groove, so that the pipe can be inserted smoothly.